Asset Impairment and Mine Closure Costs (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) operating_complex	Sep. 30, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Number of operating complexes | operating_complex				2
Asset impairment and mine closure costs	$ 2,120,292	$ 19,100	$ 5,060	$ 2,139,438	$ 6,572
Fair value of impaired assets	470,600			$ 470,600
Impairment of mining complex		5,600
Royalty Agreements [Member]
Restructuring Cost and Reserve [Line Items]
Impairment of advance royalty		$ 12,200
APP [Member]
Restructuring Cost and Reserve [Line Items]
Asset impairment and mine closure costs	1,700,000
Other Segments [Member]
Restructuring Cost and Reserve [Line Items]
Asset impairment and mine closure costs	$ 400,000